Xerography is defined by Wikipedia as "is a dry photocopying technique invented by Chester Carlson in 1938, for which he was awarded U.S. Patent 2,297,691 on October 6, 1942. Carlson originally called his invention electrophotography. It was later renamed xerography� — from the Greek roots xeros "dry" and -graphia "writing" — to emphasize that, unlike reproduction techniques then in use such as cyanotype, this process used no liquid chemicals."

Xerography works similiarly, it is dry writing. It doesn't require you to write anything special other then your xerography config (and that is only if you don't want to use the defaults)

Themes are seperate node.js repositories. By default, Xerography installs Xerography-Peppercorn-Saison so that you have a theme to begin with. For now, take a look at Xerography-Peppercorn-Saison so you can see how to build your own theme.